At present, conventional bearings that use lubricant or lubricating grease for lubrication during their operation have great limitations in some special occasions of use. For example, for bearings for underwater operation, the lubricant or lubricating grease replenishment, maintenance and so on are very difficult. Besides, if conventional lubricant or lubricating grease is used in equipment for producing food or drug, etc., the products may be contaminated easily, resulting in unqualified products. In addition, for mechanical equipment used in high dusty environment, such as some equipment in industrial and mining enterprises will operate under very harsh conditions, many problems will be brought to the normal use of the mechanical equipment if the conventional lubrication method is used, resulting in severe frictional wear or even damage or failure of the moving parts. Therefore, it is necessary to develop a self-lubricating fabric that can be applied to mechanical moving parts in replacement of conventional lubricant and lubricating grease.
As the science and technology is developed rapidly, oil-free lubrication bearings that employ pure polytetrafluoroethylene resin (PTFE resin) as pressed faces have been developed successively. However, in the actual application process, since PTFE has very low surface energy and the strength of bonding with the metal substrate material is poor, the PTFE layer may flake off easily when using; besides, since PTFE resin has a drawback of cold flow and may be deformed irreversibly under the action of external force, the PTFE resin layer may be worn out easily when PTFE resin is used as a self-lubricating material in a bearing. Especially, under high load operating conditions, the bearing may be fractured easily, and even may threaten the life safety of the operator.
For example, in Chinese Patent Document No. CN102535167A, a self-lubricating composite material liner for bearing and a producing method thereof are disclosed. The self-lubricating composite material liner is a fiber fabric woven from PTFE fibers and at least one other fiber, with an impregnating material clad on the surface of the fiber fabric woven. Though the impregnating material attains an effect of reducing friction and wear, the impregnating material is clad on the entire fiber fabric woven through a spreading-rolling process. As a result, the surfaces of the PTFE fibers are impregnated with resin. Consequently, the self-lubricating property is degraded, and the molybdenum disulfide, nanometer alumina, and super-fine fluorinated resin powder constituents in the impregnating material are difficult to be uniformly distributed in the fiber fabric woven, resulting in instable abrasion proof of the self-lubricating composite material liner and therefore affecting the long-time stable use of the bearing.
In Chinese Patent Document No. CN102597073A, a sliding surface material and a multi-layer sliding part having the sliding surface material is disclosed. The sliding surface material is formed by impregnating phenolic resin into a reinforcing substrate formed from a woven fabric, wherein, the woven fabric is formed of warp yarns and weft yarns, which are twisted yarns obtained by doubling and twisting a single twist yarn that contains fluororesin fibers and a single twist yarn that contains polyester fibers. Though the invention realizes low swelling property in wet environment (e.g., water) and frictional wear property under the same conditions, the yarns used for the reinforcing substrate of the sliding surface material are produced by doubling and twisting a single twist yarn of fluororesin fibers and a single twist yarn of polyester fibers, which are equivalent to each other in terms of diameter. Consequently, the fluororesin fibers and polyester fibers are exposed in almost the same proportion on a side of the material. Then, since the proportion of fluororesin fibers in the sliding surface is low, the self-lubricating property of the sliding surface material is affected directly, the local temperature will be increased rapidly during friction, and the wearing of the sliding part will be accelerated.
In Japanese Patent Document No. 1987-79112, a belt that is of a conveyer belt type is disclosed. The surface of the belt is provided with reinforcing fabric texture formed from PTFE fibers and/or a PTFE fiber layer containing heat-resistant fibers. Though the belt in the invention has good anti-stripping performance, excellent heat resistance performance, and elongation resistance performance, when it is used to convey objects, a core-sheath yarn structure and a double-layer fabric texture scheme have to be used to attain those effects. The core-sheath yarn structure employs PTFE fibers for sheath yarn and heat-resistant fibers for core yarn, and the core-sheath yarns are used as surface warp yarns in the weaving process. Consequently, the thickness of the resultant fabric is too great, and the overall deformation of the fabric is severe under the action of external force, causing compromised dimensional stability. Besides, in the weaving process, relative slippage between the core yarn and the sheath yarn may occur in the surface warp yarns and consequently the core yarns may be exposed under the action of external force in the beam-warping and weaving procedures. When the belt is used to convey objects, the belt may adhere to the conveyed objects, resulting in product failure.